Mediterranean intense desert dust outbreaks and their vertical structure based on remote sensing data

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Gkikas, Antonis, Basart, Sara, Hatzianastassiou, Nikos, Marinou, Eleni, Amiridis, Vassilis, Kazadzis, Stelios, Pey, Jorge, Querol, Xavier, Jorba, Oriol, Gassó, Santiago, Baldasano, José M.
• Other Authors: Barcelona Supercomputing Center
• Format: Article in Journal/Newspaper
• Language: English
• Published: European Geosciences Union (EGU) 2016
• Subjects: Àrees temàtiques de la UPC::Enginyeria biomèdica; Dust storms; Mediterranean Sea > Environmental conditions; Satellite meteorology; Mediterranean dust outbreaks; Remote sensing data; Satellite CALIPSO; AErosol RObotic NETwork; Pols; Mediterrània; Mar; Aerosol Robotic Network
• Online Access: http://hdl.handle.net/2117/88849; https://doi.org/10.5194/acp-16-8609-2016

The main aim of the present study is to describe the vertical structure of the intense Mediterranean dust outbreaks, based on the use of satellite and surface-based retrievals/measurements. Strong and extreme desert dust (DD) episodes are identified at 1° × 1° spatial resolution, over the period March 2000–February 2013, through the implementation of an updated objective and dynamic algorithm. According to the algorithm, strong DD episodes occurring at a specific place correspond to cases in which the daily aerosol optical depth at 550 nm (AOD550 nm) exceeds or equals the long-term mean AOD550 nm (Mean) plus two standard deviations (SD), which is also smaller than Mean+4 × SD. Extreme DD episodes correspond to cases in which the daily AOD550 nm value equals or exceeds Mean+4 × SD. For the identification of DD episodes, additional optical properties (Ångström exponent, fine fraction, effective radius and aerosol index) derived by the MODIS-Terra & Aqua (also AOD retrievals), OMI-Aura and EP-TOMS databases are used as inputs. According to the algorithm using MODIS-Terra data, over the period March 2000–February 2013, strong DD episodes occur more frequently (up to 9.9 episodes year−1) over the western Mediterranean, while the corresponding frequencies for the extreme ones are smaller (up to 3.3 episodes year−1, central Mediterranean Sea). In contrast to their frequency, dust episodes are more intense (AODs up to 4.1), over the central and eastern Mediterranean Sea, off the northern African coasts. Slightly lower frequencies and higher intensities are found when the satellite algorithm operates based on MODIS-Aqua retrievals, for the period 2003–2012. The consistency of the algorithm is successfully tested through the application of an alternative methodology for the determination of DD episodes, which produced similar features of the episodes' frequency and intensity, with just slightly higher frequencies and lower intensities. The performance of the satellite algorithm is assessed against surface-based daily ...